Rotary cutters using cooperating rollers for performing transverse cuts on a web of printed paper product are widely used in the printing industry. Such devices typically have longitudinally extending knives protruding out from the surface of one or both of the cooperating rollers, with at least one of the rollers serving as an anvil spaced apart so as to be slightly contacted by the opposing knife roller. The circumference of the cutting roller is normally a fixed dimension longer than the multiple repeat length of the product material being cut and not an exact multiple thereof so that a pair of transverse cuts may be required between adjacent units. This results in production of transverse strips or "chips" of material, which must be removed from the cutting area and disposed of in order to avoid interference with delivery of the finished units or products.
Use of impalement pins for grasping chips and removing them from the cutting are of a rotary cutter is disclosed in several prior art patents. U.S. Pat. No. 3,893,359, issued Jul. 5, 1975, to Gregoire, discloses placement of sharpened pins on an anvil roller that cooperates within an opposing cutting roller, the pins impaling transversely cut chips at the cutting area between rollers and conveying them around and away from the cutting area where they are removed from impalement by coming into contact with stripping fingers adjacent to the back side of the anvil roller. U.S. Pat. No. 4,846,030, issued Jul. 11, 1989, to McMahon et al., discloses mounting of impalement pins on a disc which brings the pins into engagement with chips as they are cut. The impaled chips are removed from the pins by being contacted with an abuttment member such as a moving belt. U.S. Pat. No. 4,691,603, issued Sep. 8, 1987, to Winnemoller, discloses extensible needles for piercing material that is to be removed by a cutter, the needles being serrated for providing frictional grasping engagement. None of these references discloses a specific shape for the pins or needles except that they are pointed and in one case provided with serrations.
Impalement pins as employed in prior art devices exemplified by the referenced patents have relied upon relatively deep impalement to secure chips for removal away from the cutting area, the pins typically being arranged to stab the chips to a depth of 1/8 inch. While providing for effective grasping of the chips, this makes for difficulty in removing them from the pins. In the case of devices using a mechanical comb-like stripper with fingers placed between the cylinder and the chip, linear placement and spacing are very critical, and jamming occurs frequently. Another approach is to use a rotating wheel onto which are mounted pins that are moving both faster than and timed to the chip. The pins on the wheel stab the chip and rip it loose from the pins on the roller. This requires perfect timing and further apparatus to strip the chips from the wheel. The pins tend to break and to be ineffective in transferring the chips from the roller to the stripper wheel. A still further method uses pins that are mounted in the cylinder so as to be retractable to release the chip. While providing for effective release of chips, the required retraction mechanism is expensive and difficult to manufacture.
Rectangular-shaped spears obtained by cutting off a transverse section of a perforation rule are used instead of round pins in rotary cutters made by Baldwin Technology. These spears at their chip-engagement end have a double-bevelled sharp edge parallel to and spaced apart halfway between edges of side faces of the spear. Spears with this geometry at their chip-impalement ends do not form a bent-over barb that would retain chips, but rather become slightly flattened out upon contacting the surface of an opposing roller. Retention of chips is provided for by deep penetration as described above.
It is desired to provide chip-impalement spears that may be arranged to grip chips lightly but effectively facilitating controlled removal of the chips and avoiding problems associated with prior art approaches.